Backhead and check valve for down-hole drills

Abstract

A check valve system is for a fluid-actuated percussive drill assembly including a casing, a backhead connected with and extending into the casing, and a fluid distributor disposed within the casing. The backhead has a central axis, a supply passage extending along the axis, and an outer surface section extending circumferentially about the axis and disposed within the casing. The check valve system includes a port extending between the outer circumferential surface section of the backhead and the supply passage. Preferably, several ports are spaced circumferentially about the backhead outer surface. An annular check valve is disposed about the outer circumferential surface section of the backhead and is configured to alternately permit fluid flow through the backhead port and substantially seal the backhead port. At least a portion of the check valve is movable between a first position, where the check valve portion is disposed across and generally obstructs the backhead port, and a second position, where the check valve portion is spaced from the backhead port. The backhead body has an inner end disposed within the casing and a recess extending into the body from the end and generally along the central axis, the recess being sized to receive the a portion of the fluid distributor portion so as to generally retain the distributor at a desired position within the casing.